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    <title>glViewport - OpenGL ES 3.2 Reference Pages</title>
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    <div class="refentry" id="glViewport">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>glViewport — set the viewport</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">void <strong class="fsfunc">glViewport</strong>(</code>
              </td>
              <td>GLint <var class="pdparam">x</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLint <var class="pdparam">y</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLsizei <var class="pdparam">width</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLsizei <var class="pdparam">height</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term"><em class="parameter"><code>x</code></em>, </span>
              <span class="term">
                <em class="parameter">
                  <code>y</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specify the lower left corner of the viewport rectangle,
                    in pixels. The initial value is (0,0).
                </p>
            </dd>
            <dt>
              <span class="term"><em class="parameter"><code>width</code></em>, </span>
              <span class="term">
                <em class="parameter">
                  <code>height</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specify the width and height
                    of the viewport.
                    When a GL context is first attached to a window,
                    <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> are set to the dimensions of that
                    window.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            <code class="function">glViewport</code> specifies the affine transformation of
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math>
            and
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math>
            from
            normalized device coordinates to window coordinates.
            Let
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mfenced open="(" close=")">
                    <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                    <mml:mi mathvariant="italic">nd</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                    <mml:mi mathvariant="italic">nd</mml:mi>
                    </mml:msub>
                </mml:mfenced>
            </mml:math>
            be normalized device coordinates.
            Then the window coordinates
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mfenced open="(" close=")">
                    <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                </mml:mfenced>
            </mml:math>
            are computed as follows:
        </p>
        <p>
            </p>
        <div class="informalequation">
          <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mfenced open="(" close=")">
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                                <mml:mi mathvariant="italic">nd</mml:mi>
                                </mml:msub>
                                <mml:mo>+</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:mfenced>
                        <mml:mo>⁢</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:mfrac>
                                <mml:mi mathvariant="italic">width</mml:mi>
                                <mml:mn>2</mml:mn>
                            </mml:mfrac>
                        </mml:mfenced>
                        <mml:mo>+</mml:mo>
                        <mml:mi mathvariant="italic">x</mml:mi>
                    </mml:mrow>
                </mml:mrow>
            </mml:math>
        </div>
        <p>
        </p>
        <p>
            </p>
        <div class="informalequation">
          <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mfenced open="(" close=")">
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                                <mml:mi mathvariant="italic">nd</mml:mi>
                                </mml:msub>
                                <mml:mo>+</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:mfenced>
                        <mml:mo>⁢</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:mfrac>
                                <mml:mi mathvariant="italic">height</mml:mi>
                                <mml:mn>2</mml:mn>
                            </mml:mfrac>
                        </mml:mfenced>
                        <mml:mo>+</mml:mo>
                        <mml:mi mathvariant="italic">y</mml:mi>
                    </mml:mrow>
                </mml:mrow>
            </mml:math>
        </div>
        <p>
        </p>
        <p>
            Viewport width and height are silently clamped
            to a range that depends on the implementation.
            To query this range, call <a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument
            <code class="constant">GL_MAX_VIEWPORT_DIMS</code>.
        </p>
      </div>
      <div class="refsect1" id="errors">
        <h2>Errors</h2>
        <p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if either <em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em> is negative.
        </p>
      </div>
      <div class="refsect1" id="associatedgets">
        <h2>Associated Gets</h2>
        <p>
            <a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_VIEWPORT</code>
        </p>
        <p>
            <a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAX_VIEWPORT_DIMS</code>
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>API Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
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              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="4">
                <span class="bold"><strong>OpenGL ES API Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.1</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.2</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">glViewport</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="glDepthRangef.xhtml"><span class="citerefentry"><span class="refentrytitle">glDepthRangef</span></span></a>
        </p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 1991-2006 Silicon Graphics, Inc.
            Copyright <span class="trademark"/>© 2010-2015 Khronos Group.
            This document is licensed under the SGI Free Software B License.
            For details, see
            <a class="link" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p>
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